The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Materials with hierarchical porosity find applications in a wide range of technologies. Such applications may involve catalysis, desalination, energy storage and conversion, thermal and acoustic insulation applications, and filtration applications as sorbents for water purification, just to name a few. Aerogels, foams and ordered arrays of hollow spheres are desirable for such applications, with aerogels being especially desirable. Aerogels are microporous and mesoporous (pores <300 nm), ultra-lightweight materials that can achieve surface areas in excess of 3000 m2/g. Because of these characteristics, they are ideally suited for the above listed technologies and applications.
Aerogels are made via the sol-gel process in which a reaction solution is gelled and the solvent is extracted. The solvent is extracted in such a way as to leave the porous, solid matrix intact. Though the pore sizes of aerogels can typically be tuned somewhat by varying the synthetic parameters of the sol-gel process, limitations do exist. The hierarchical nature of the porosity (e.g. pores on several size scales) allows these materials to simultaneously achieve high surface areas (pores <2 nm), and fast mass transport (pores >1 micron) leading to improved performance in relevant applications, such as catalysis. The techniques used to achieve these materials are typically limited in either the range of pore sizes that can be achieved and/or the time/cost of the process. Accordingly, there is still a strong interest in a method that can be carried out rapidly, and which is able to precisely tailor materials to have a hierarchy of pore sizes. In particular, there is a particularly strong interest in tailoring a system and method that can be used to produce an aerogel having pores ranging from less than about 2 nm in diameter to greater than about 100 microns in diameter. There is also a strong interest in a new system and method which enables an aerogel to be formed which has an improved hierarchy of pore sizes, a greater range of pore sizes, and the ability to form the aerogel such that pores of selected sizes can be placed (i.e., formed) at specific locations of the aerogel.